High speed drill bit



Nov. 24, 1964 G. BARON ETAL 3,158,216 HIGH SPEED DRILL BIT Filed April 20, 1962 e Sheeis-Sheet 1 1 I INVENTORS GUY .BARON F'!!- 1 ANA r045 VERON/VEAU BYW ATTORNEYS Nov. 24, 1964 s. BARON ETAL v 3, 5 ,2 6 HIGH SPEED DRILL BIT Filed April 20, 1962 6 Sheets-Sheet 2 INVENTORS 6U Y BARON ANATOLE VERO/VNEAU BY; I

ATTORNEYS Nov. 24, 1964 G, BARON ETAL 6 Sheets-Sheet .3

, INVENTORS GUY BARON ANATOLE VER0/V v54 Nov. 24, 1964 BARON ETAL HIGH SPEED DRILL BIT 6 Sheets-Sheet 4 Filed April 20, 1962 Fig. 9

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INVENTORS GUY BARON ANATOLE VERO/VNMU ATTORNEY5 Nov. 24, 1964 G. BARON ETAL HIGH SPEED DRILL BIT 6 Sheets-Sheet 5 Filed April 20, 1962 INVENTORS GU Y DARON ANA TOLE VERO/VA/EAU Fl .41 I

ATTORNEYS Nov. 24, 1964 G. BARON ETAL HIGH SPEED DRILL BIT 6 Sheets-Sheet. 6

Filed April 20, 1962 INVENTORS GUY BARON ANATOLE VERONNEAU ATTORNEYS United States Patent 3,153,216 EEGH SFEEB DRILL BIT Guy Baron, Colornhes, and Anatole Veronneau, Dourdan, France, assi nors to Institut Francais du Pen-ole des Carlin-rants et Lubrifiants, Rueildtialmaison, Seine et- (Else, France Filed Apr. 20, 1962, er. No. l89,tl52 Glairns priority, application France Apr. 27, 1961 18 Elairns. (til. 175-402) The present invention relates to a drill bit which may be operated at high rotary speeds while simultaneously obtaining a satisfactory removal of the drill cuttings or debris.

Up to the present time the drill bits acting by abrasion eilect could not be operated at high rotary speeds of 600 rpm. or more since at such speed the removal of the cuttings is inadequate. Consequently, the bits cannot penetrate substantially into the earth formations. Such a stufiing phenomenon results in a practical ineffectiveness of the drill bit at such rotary speeds.

Moreover, the drill bits of this type, which are presently available, must be provided with diamond cutting parts which are very expensive.

It is therefore an object of this invention to provide a drill bit, acting by abrasion effect like a rasp, which may be manufactured at relatively low cost by use of cutting parts thereon which are cheaper than diamonds.

It is another object of this invention to provide a drill bit of this type which may be operated at high rotary 9 speeds of, for instance, up to 1500 or more.

It is still another object of this invention to provide a drill bit wherein the wear is substantially uniformly distributed over the various cutting parts so as to obtain a longer operating life of the bit without the necessity of replacing some particular cutting parts which wear rapidly.

It is a further object of this invention to provide a drill bit for rapidly removing the debris or cuttings, even when operated at high rotary speeds.

It is still a further object of this invention to provide a drill bit the cutting parts of which may be replaced without requiring any chan e or replacement of the remaining parts of the bit.

These and other objects as may be apparent from the following specification and with reference to the accompanying drawings constituting a part thereof, as well as from the appended claims, are achieved by the drill bit according to the present invention comprising a support having the shape of a paraboloid provided with an inner central recess and, if desired, with adjacent holes opening at the head of the bit. These holes are provided for a passage of the drilling fluid. The external surface of the bit is provided with cutting parts secured in the external wall of the support in such a manner so as to emerge by a constant height above said surface,

The invention will be further explained in detail with reference to the accompanying drawings, wherein FIGURE 1 is a side perspective view of a simplified embodiment of the drill bit according to the present invention;

FIGURE 2 shows the same drill bit as in FIGURE 1 from beneath along a direction slightly inclined with respect to its axis, said drill bit further comprising a central cutting blade and auxiliary ports for the passage of the drilling fluid;

FIGURE 3 dlagramarntically represents the position of the cutting parts of the bit (hatched on the drawing) into the rock, during the drilliru operation;

FIGURE 4 schematically represents a side view of the drill bit;

FIGURE 5 illustrates the passage-Way of the drilling fluid when the bit is not revolving;

FIGURE 6 shows the variations of the passage sections of the drilling fluid between the cutting parts positioned in a plane perpendicular to the bit axis, as a function of the elevation of this plane;

FIGURE 7. schematically shows the passage sections between the rock and the bit at a certain level of the latter;

FIGURE 8 shows at diiterent levels of the bit the speed tangential component of the cutting parts of the bit with respcc to the rock, which is the same as that of the debris with respect to the bit;

FIGURE 9 shows at different levels of the bit the resultant of the speed components to which the cuttings are subjected;

FIGURE 10 illustrates thepassage-way of a piece of debris or drill cutting in the absence of obstacles;

FIGURE 11 represents a vertical sectional view of a bit of the type shown in FIGURE 1, having its central recess provided with a cutting blade according to this invention for breaking upthe core, projected on a plane perpendicular thereto, and

FIGURES 12 and 12A illustrate an embodiment of the cutting blade according to this invention, constituted by two cutting elements positioned apart from each other, in a common metal piece, for instance of steel.

The drill bit according to this invention is essentially characterized by the cutting parts a projecting above the external surface of the support by such an amount so as to provide therebetween a suiticient clearance for draining off the drill cuttings or debris and that this clearance is oriented in the direction corresponding, preferably with accuracy, to the normal trajectory of the debris at the average speed at which the drill bit is to be operated.

FIGURE 3 shows the clearance spaces formed between the lower part of the bit and the rock into which the cutting parts are penetrating.

The amount of cutting parts per surface unit of the bit is so selected as to realize a compromise between the ability to rock breaking, which is directly related to said amount, and the capacity of draining off the cuttings, which is inversely related thereto.

This selection must be made in consideration of the operating conditions of the bit and particularly the weight to be applied thereto.

FIGURE 4 represents a side View of the drill bit according to this invention. In this figure the external profile AB corresponds to a portion of a parabola and the inner profile AC to another portion of a parabola joined to the corresponding generatrix CD of the inner cylindrical central pipe conveying the drilling fluid.

As a result of the selected inner profile a short core is formed which is progressively broken up by the cutting parts provided, on the inner surface joining with the pipe, for the drilling fluid and/ or by the cutting blade provided in the central recess, as shown in FIGURE 2.

The drilling fluid is conveyed along the trajectory shown by the arrows in FIGURE 5.

By pressure etfect it goes up through the space between the rock and the bit along a direction which, when the bit is not rotated, is that of the generatrixes or meridians AB.

The passage sections or clearance spaces at available between the cutting parts a are increasing in proportion of'the radius r ofthe circle corresponding to a crosssection of the paraboloid along a plane perpendicular to its axis (FIGURE 6).

FIGURE 7 shows the clearance spaces d provided between the cutting parts at a given level of the bit, i.e. in a given plane perpendicular to its axis.

The height of the cutting parts above the support (FIGURES 3 and 7) may be varied according to the size of the bit, the nature of the drilled earth formations, the hardness and brittleness of the cutting parts and the expected efliciency, etc.

Thus, a given height e of the cutting parts above the support, which is suflicient for drilling in a hard rock in view of the low amount of debris to remove per unit time, may be found greatly insuflicient for drilling in a relatively soft rock, which requires draining oil a greater amount of debris. In the latter case, the bit tends to get clogged (stufllng phenomenon) and, accordingly, gets hot and worn and finally does not have any efficiency.

It has been observed by experience that a height of at least 2 mm. of the cutting parts above the support is required for obtaining the benefit of the advantages of this invention. The size of the debris, depending on the depth drilled per revolution of the bit, is usually small enough with respect to the clearance spaces formed be tween the cutting parts to facilitate the draining oil of said debris with the drilling fluid stream.

Additionally, the removal of the debris or cuttings is facilitated by use of a particular relative positioning of the cutting parts with respect to each other. Accordingly, one of the essential features of this invention consists in the positioning of the cuttin parts substantially along helical spirals of variable pitch on the external surface of the support having the shape of a paraboloid.

The type of helical spiral to be used depends on the range of the operating speeds of the bit. It will be generally determined on the basis of the mean value of this range and of the discharge rate of the drilling fluid selected so as to correspond to a mean drilled depth per unit time. This spiral remains generally effective, other factors being constant, for lower drilling speeds wherein a correspondingly smaller amount of debris or cuttings is to be drained off. This spiral is more effective when the discharge rate of the drilling iluid is adjusted so that the direction of the speeds resultant (speed of the drilling fluid and peripheral speed of the bit) is only slightly changed.

The discharge rate of the drilling fluid may also be adjusted so as to facilitate the removal of the cuttings at rotary speeds of the bit higher than its designed speed.

FIGURES 6 to 8 illustrate the speed components on which is based the determination of the curvature of the helical spiral according to this invention. This helical spiral must correspond to the normal trajectory of the debris as a result of the effect of both'the circulating speed of the drilling fluid and the rotary speed of the bit.

FIGURE 8 shows at different levels of the bit, along the same meridian, the peripheral speed component U to U of the debris or cuttings with respect to the bit (which component is equal in value to the peripheral speed of the cutting parts of the bit with respect to the rock, but of opposite direction).

FIGURE 9 illustrates, also along a given meridian and at diflerent levels of the bit, the combined action of a constant speed V of the drilling fluid circulation, oriented upwardly along said meridian and of the variable peripheral speeds U to U which results in variable directions of the resultants W to W at the different levels.

FIGURE 10 illustrates the shape or" the envelope curve of the different vectors'W. This envelope is a helical spiral of variable pitch corresponding to the minimum travel of the stream of flushing fluid and the debris or cuttings drained 0E therewith.

In the case of zero rotary speed, as illustrated in FIG- URE 5, the drilling fluid passes upwardly on the side along a generatrix such as AB, at a speed V through the annularclearance spaces 0! (FIGURES 6 and 7). The value of V depends in particular on the passage section S of the fluid between the bit and the rock, i.e. on the sum of the clearance spaces d. In the case illustrated in FIG- A URE 7, for instance, the value of the total passage section S is given by the formula wherein r represents the radius of the considered annulus, e the height of the cutting parts above the support and a a coefficient expressing the proportion of the annular space covered by the cutting parts.

The value of V, equal to (wherein D represents the discharge rate) may be kept substantially constant at the diiferent levels of the bit in spite of the variation of r provided that the value of e and/or a is correspondingly adjusted. If, on the contrary, the values of e and of a are kept constant, the speed V decreases with an increasing radius r and the speed resultant is less inclined with respect to the plane perpendicular to the bit axis (lower value of angle 7). This results in a longer travel for draining ofi the cuttings to the upper part of the bit. Finally, the direction along which the cutting parts are to be placed not only depends on the rotary speed of the bit and on the discharge rate of the drilling fluid, but it also depends on the density of population of the cutting parts (coeflicient a) which is generally so selected as to distribute the working strains as uniformly as possible over the various cutting parts.

According to the particular embodiment shown in FIG- URE l, the cutting parts are distributed on equidistant parallels corresponding to sections of the drill bit by planes perpendicular to its axis and the number of cutting parts on each parallel increases in proportion to the radius r of the circle constituting this parallel. This is justified in view of the fact that the greater the rock surface in contact with each cutting part during one complete revolution of the bit, the more important the work of the latter. This work has therefore to be distributed over a greater number of cutting parts so as to provide for a substantially constant wear of the same value as that of the cutting parts at other levels of the bit corresponding to a smaller radius r,;.

In practice, there will necessarily be a certain discontinuity in the ratio of the number of cutting parts to the radius of the circle along which they are placed since the number of cutting parts cannot be varied by less than one unit.

However, it is not necessary to keep this ratio subtantially constant and the efifective wear at the different levels of the bit will be taken into account by adding, if convenient, supplementary cutting parts at the levels where the wear is the most important. Thus, there may be provided a greater density of population of the cutting parts at the head of the bit which may bear a greater part of the weight applied to the bit. This is illustrated in FIGURES 1 and 2.

The same FIGURES l and 2 show channels for the removal of the debris or cuttings which are oriented along the same type of helical spiral as the cutting parts. These channels (K K and K are provided in the external wall of the support so as to make easier the removal of the debris when, as a consequence of the wear of the cutting parts, the annular space formed between the envelope of the heads of the latter and the support has been reduced. Such provision of channels provides means for draining oil with the minimum travel a substantial part of the debris formed by said cutting parts.

The removal of the other debris and particularly that formed by those cutting parts which are not positioned just before a draining channel, will be facilitated by means. of a convenient distribution of the cutting parts so as to provide at each parallel (i.e. at each level of the bit comprising cutting parts) a free space between the the depth drilled during one revolution of the bit in the rock must be 0.4 mm. at a rotary speed of 1500 rpm and the average size of the cuttings will be of the same order, although some of them may have a greater size of,

for instance, 1 mm. but rarely more.

Such a size of the cuttings is still low with respect to the clearance section between the bit and the rock, depending on the height of the cutting parts above the support.

Accordingly, the considered penetration rate is easily achievable and even higher rates would not lead to such diiiiculties for the removal of the cuttings as that resulting in the accumulation of 'the same in the bore hole hereabove referred to as a stuffing phenomenon responsible for a practical inefiiciency of the drilling operation.

The above mentioned characteristics of a particular drill bit according to this invention are given for illustrative purposes only and it is obvious to any one skilled in the art that the particular details of size of the bit, equation of the paraboloid, height of the cutting parts above the support, density of population of the same as well as theshape of the helical spiral may be modified according to the type of earth formation drilled, the nature of the cutting parts, the rotary speed of the bit or individual preference, without departing from the spirit of this invention and the scope of the appended claims.

What is claimed as this invention is:

1. A drill bit operable at high rotary speeds, and comprising a support member having an external surface substantially shaped as a paraboloid and having a central recess adapted for the tormation or a core thereinto, said support being provided with cutting parts projecting by an even height above said external surface which is at least equal to 2 millimeters, said cutting parts being positioned on said external surface along the direction of a helical spiral of varying pitch.

2. A drill bit according to claim 1 and further comprising discharge channels in the external wall of said support substantially along the direction of a helical spiral of varying pitch for the passage of cuttings therethrough.

3. A drill bit according to claim 1 wherein the helical spiral of varying pitch along the direction of which are positioned the cutting parts is the envelope curve of the resultant at each drilling fluid and the peripheral speed of the bit at said level.

4. A drill bit according to claim 2 wherein the helical spirtl of varying pitch along the direction of which are oriented the discharge channels is the envelope curve of 1 the resultant at each level of the bit of the velocity of the drilling fluid and the peripheral speed of the bit at said level.

5. A drill bit according to claim 2 wherein the cutting level of the bit of the velocity of the parts are distributed at different levels of the bit correr sponding to planes perpendicular to the bit axis.

6. A drill bit according to claim 5 wherein the different levels at which the cutting parts are distributed correspond to equidistant planes. 1

7. A drill bit according to claim 5 wherein the cutting parts at each level are so distributed that a major thereof is provided just before a discharge channel.

8. A drill bit according to claim 5 wherein at each level the cutting parts are distributed in a plurality of groups each comprising several cutting parts positioned close to each other and separated by such an interval so as to provide a suflicient section passage for the cuttings therebetween.

9. A drill bit according to claim 5 wherein at each level the cutting parts are distributed in a number of groups equal to the number of discharge channels with only one group being provided within the interval between two successive channels at said level, said one group being positioned in the vicinity of the second of said two discharge channels with respect to the revolving direction of the bit so that the space between said one group and the first channel is kept free for the passage of the cuttings.

10. A drill bit according to claim 5 wherein the different levels at which the cuttings parts are distributed correspond to equidistant planes spaced from one another by such intervals so as to provide a sufiicient section passage for the cuttings.

11. A drill bit according to claim 5 wherein at each level the cutting parts are distributed in a plurality of groups, said groups being staggered with respect to the closer groups of the adjacent levels.

12. A drill bit according to claim 1 wherein a flat cutpart ting blade of a high degree of hardness is secured on the wall of the central recess of the bit so as to break up the core as it is formed.

13. A drill bit according to claim 12 wherein the lower end of the cutting blade is V-shaped and the angle formed by the two arms of the V is between and 170.

14. A drill bit according to claim 12 wherein the lower end of the cutting blade is V-shaped and the angle formed by the two arms of the V is between and 15. A drill bit according to claim 12 wherein the cutting blade comprises at least one cutting part bedded in a sheath made of steel.

16. A drill bit according to claim 12 wherein the maximum diameter of the central recess is 4 centimeters.

17. A drill bit according to claim 12 wherein the maximumthickness of the cutting blade is equal to one fourth of the diameter of the central recess.

18. A drill bit according to claim 1, further comprising auxiliary discharge channels opening at the lower part of the bit in the vicinity of the actual surface being cut for the passage of the drilling fluid.

References Cited in the file of this patent UNITED STATES PATENTS 2,493,178 Williams Jan. 3, 1950 2,673,717 Bacon Mar. 30, 1954 2,838,284 Austin June 10, 1958 2,838,286 Austin June 10, 1958 3,058,535 Williams Oct. 16, 1962 FOREIGN PATENTS 1,197,183 France June 1, 1959 

1. A DRILL BIT OPERABLE AT HIGH ROTARY SPEEDS, AND COMPRISING A SUPPORT MEMBER HAVING AN EXTERNAL SURFACE SUBSTANTIALLY SHAPED AS A PARABOLOID AND HAVING A CENTRAL RECESS ADAPTED FOR THE FORMATION OF A CORE THEREINTO, SAID SUPPORT BEING PROVIDED WITH CUTTING PARTS PROJECTING BY AN EVEN HEIGHT ABOVE SAID EXTERNAL SURFACE WHICH IS AT LEAST EQUAL TO 2 MILLIMETERS, SAID CUTTING PARTS BEING POSITIONED ON SAID EXTERNAL SURFACE ALONG THE DIRECTION OF A HELICAL SPIRAL OF VARYING PITCH. 